EP1219375B1 - Method for repairing damaged areas on a metallic workpiece - Google Patents

Description

Technical area

The invention relates to a method for repairing superficial, by a loss of material formed damage to a metal component, according to the preamble of claim 1, see, for. See, for example, US-A-4,381,944.

State of the art

Metal components, such as e.g. the blades or other components of a Turbomachine, in particular a turbine or a compressor can high stresses due to oxidation and / or corrosion and / or erosion and / or abrasion. Especially with turbine blades can these stresses on the surface of the blades local to one Material loss or material removal, resulting in damage, especially in the form of relatively large depressions or holes, form. Due to high prices for new blades, one strives for this Damage to the blades to repair, on the one hand their strength and on the other hand to restore their flow quality. One way, the To repair damaged areas or the component, is the damaged areas to be filled by means of a high-temperature soldering process. In a conventional The procedure becomes a common metal solder in the high-temperature soldering process used, which wets a metallic surface and a soldering one Diffusion compound enters with the metallic surface. To fill up relatively large-scale defects are called "wide-gap solders" or "WideGap-Lot" used; These are metallote, to which a metal filler is added is, this metal filler preferably similar properties as the metal of the metal component.

In particular, by the oxidative and corrosive stress of a Metal components may be at or in the damaged nonmetallic Reaction products, e.g. Form oxides or nitrides. As a usual Metal solder does not wet non-metallic surfaces and with these also no Diffusion compound incoming, it is to carry out the soldering process imperative, the filled-in damaged areas of these to clean non-metallic reaction products, for example by Sanding or sandblasting. However, it has been shown that by a conventional high-temperature soldering applied fillings, in particular on the highly stressed turbine blades, in some cases none have satisfactory durability, so that after a relatively short Service life in the field of repairs may again come to damaged areas.

US 5 334 344 shows a method for soldering a ceramic part, a Single crystal and a metal part on a single crystal or a ceramic part a metal part or a single crystal on a metal part, wherein for the production the solder joint is an active solder used. Under an "active lot" becomes a Alloy understood that at least one element, such. Titanium, that contains an affinity for non-metals, e.g. Oxygen, nitrogen, so that during the soldering process no flux are required. An active solder thus has the special property, both metallic and non-metallic To be able to wet surfaces and when soldering with a non-metallic Surface a reaction compound and when soldered with a metallic Surface to be able to enter a diffusion connection.

Presentation of the invention

The present invention is concerned with the problem of a method of the aforementioned type so that a subsequently executed repair has an increased durability.

According to the invention, this problem is solved in a method of the beginning mentioned type achieved in that in a Hochtemperaturlötverfahren, with the defects are filled, an active solder is used.

The invention is based on the general idea, the advantageous Properties of an active solder, which is basically used for making a Solder connection between two components are known, now also to Filling a damaged area as part of a repair of a metal component exploit. These considerations are based on the knowledge that it is in the Repair is often not possible, the damaged areas completely from the non-metallic reaction products, e.g. Oxides, to clean. The in the respective damage site remaining residues on non-metallic surfaces can in the implementation of the high-temperature soldering of a usual metal solder are not wetted, so that in these surface sections also no diffusion connection between the metal component and the filling can be trained. These flaws or vulnerabilities in the Connection between filling and metal component reduce the durability of the Filling and thus the repair. Studies have shown that the non-metallic reaction products even after a conventional mechanical Cleaning process in the deep, barely accessible roughnesses through Corrosion, oxidation, erosion or abrasion roughened surface of the sit each damaged spot. Furthermore, it has been shown that the for the Wetting and soldering harmful non-metallic reaction products even on a completely cleaned, smooth, even surface quasi train on their own if this surface is unprotected. This can for example, during heating of the component during the cleaning process respectively; This can also occur during heating during the soldering process take place if the present furnace atmosphere is not adequately monitored is, e.g. in terms of vacuum or outgassing.

Through the use of an active solder is used in the repair of damaged areas achieved on a metal component, that the active solder in the damaged area in areas with metallic surface enters into a diffusion bond and in areas with non-metallic surface, ie in areas of disturbing Reaction products, reaction compounds builds up. Accordingly possesses The active solder has a high binding both to the metallic surfaces also on the non-metallic surfaces. Of particular importance In addition, that the active solder both metallic and non-metallic Surfaces wetted alike, so that a seamless application of the Active Lots can be easily achieved. This has a high quality filling with great durability result.

It is basically possible to complete the filling by the active solder form. Preferably, a metal filler can then be added to the active solder be used to the flow properties of this Aktivlots in a suitable Way to influence. Likewise, by a metal filler, the thermal Properties as well as the strength properties of the filling in one desired way to be influenced.

In another embodiment, the active solder may be a conventional metal solder be mixed. By enrichment of the metal solder with the active solder is the metal solder quasi activated, so that it is the non-metallic surfaces of the Wet reaction products and enter into these reaction compounds can.

However, an embodiment in which a layer of active solder on the Damage is applied, with a layer of this active solder layer a standard metal solder is applied. This can be done in layers Application of active solder and metal solder successively or quasi simultaneously be performed. This procedure results in a Overall coating, which at the surface of the damaged areas a high Concentration of active solder possesses, whereby the active solder with increasing distance from the surface of the damaged area passes into the metal solder.

According to one embodiment of the method, the active solder layer and the Metal solder layer are soldered in a single soldering cycle. Under a "Soldering cycle" is understood here as a process in which the solder melts and the desired diffusion compounds or reaction compounds received. By soldering the active solder layer and the metal solder layer in a single Soldering cycle results e.g. a time advantage.

In an alternative development, the active solder layer can be applied before application soldered to the metal solder layer in a first soldering cycle while after the application of the metal solder layer in a second soldering the Soldered metal solder layer. In this approach, the individual Soldering cycles optimized in terms of their parameters for each layer of solder become; the parameters involved are, for example: temperature, Pressure, time, vacuum quality.

According to a preferred embodiment, the active solder and the Metal solder be formed in each case as a paste, in which case the active solder paste relative to the metal solder paste is thin. By this measure, the active solder paste better penetrate into depressions, which are due to the respective damage site have formed the prevailing surface roughness there. The active solder This can also improve the surface structure in the damaged area to adjust.

In a particular embodiment, the active solder on or in the each damaged spot can be formed by the respective Damaged first, an active metal, such as powder or granular, and then applied a standard metal solder. By This measure is applied to the damaged metal solder locally Active metal mixed, so that directly on the surface of the damaged area in Metalllot forms an active soldering area. The active solder is thus exactly in the place provided to it to achieve the desired reaction compounds is required. Active metals are, for example, titanium (Ti), hafnium (Hf), Zirconium (Zr). The application of the active metal can, for example, by Brushing or irradiation done.

Other important features and advantages of the method according to the invention emerge from the dependent claims, from the drawing and from the associated figure description with reference to the drawing.

Short description of the drawing

A preferred embodiment of the invention is shown in the drawing and will be explained in more detail in the following description.

The sole FIGURE 1 shows a sectional view through a metal component in the region of a Damaged area.

Ways to carry out the invention

According to Fig. 1 has a metal component 1, for example, a Ingredient, e.g. a shovel that can be a turbine on its surface a damaged by a loss of material 2 formed, for example, in the Use of the component 1 by an oxidative and / or corrosive and / or erosive and / or abrasive environment may arise. Around Damage point 2 is created by a surface 3 with a relatively large Roughness degree, which is indicated in Fig. 1 simplified by mountains 4 and valleys 5 is.

By a suitably aggressive environment, especially in the Area of the damaged area 2 on the surface 3 of the metal component. 1 non-metallic reaction products, e.g. Oxides, form. If the damaged area 2 is to be repaired, this is cleaned before, for example, mechanically by sandblasting and / or brushing. This is a big part of non-metallic reaction products from the surface 3 of the metal component 1 away. This cleaning of the surface 3 is regularly not complete, so that in particular in the valleys 5 of the rough surface 3 remains of the non-metallic reaction products remain. In Fig. 1, the after the Purification process remaining, non-metallic reaction products with 6 designated.

According to FIG. 1, an active solder 7 adjoins the surface 3 of the metal component 1, the after soldering in areas of the summit 4 with the existing there metallic surface of the metal component 1 diffusion compounds 8 enters. In contrast, the active solder 7 goes in areas of the valleys 5 with the non-metallic surfaces of the reaction products 6 reaction compounds 9 on. Accordingly, the active solder 7 has a high strength after soldering Binding to both the non-metallic reaction products 6 and the metallic surface 3 of the metal component 1. Since the non-metallic Reaction products 6 in turn via reaction compounds with the metallic Surface 3 of the metal component 1 are connected, results for the active solder 7 a seamless intensive connection to the metal component 1.

The active solder 7 is adjacent to a standard metal solder 10, which after soldering with the adjacent thereto metallic surface of the active solder 7 a Diffusion compound 11 is received. Accordingly, there is also one high-strength connection of the metal solder 10 to the active solder 7. Noteworthy Here, on the one hand, the active solder 7, both the metallic Surface portions of the metal component 1 and the non-metallic Surface sections of the reaction products 6 wetted, so that in essentially results in a closed wetting in the area of the damaged area 2. On the other hand, this has the consequence that the applied active solder 7 a has closed metallic surface by the metal solder 10th is completely wettable. This results in a high quality Filling the damaged area 2. In contrast to Fig. 1 is after soldering a Border between the active solder 7 and the metal solder 10 due to Diffusion compounds 11 usually no longer visible.

A specific embodiment of the repair method according to the invention can proceed as follows:

First, the surface 3 is cleaned in the area of the damaged areas 2. there remain from the cleaning unrecognized residues of non-metallic Reaction products 6 in particular in the valleys 5 or form there by the Heating during cleaning. Subsequently, in the area of Damage 2 applied a layer of active solder 7. The active solder 7 can as relatively thin paste present easily in the valleys 5 of the Surface roughness penetrates. Due to the special property of Aktivlots 7 wets this case both the metallic surfaces and the Non-metallic surfaces that occur in the damaged area 2. In that regard is with the active solder 7 a complete wetting of the surface 3 in the damaged area. 2 realizable.

After applying the active solder layer, a first soldering cycle can be run be in which the metal component 1 is applied together with the Active solder layer is heated. By this soldering process form the Diffusion compounds 8 and the reaction compounds 9, so that now the active solder 7 forms the surface in the damaged area 2.

As active solder 7 can be used for example: AM900, AuPdTi, AuNiTi, PdNiTi, AuTi, CuSiAlTi, AgCulnTi, AgCuHf, AgCuTi, NiZrTi, NiTi. The thickness of the applied active solder layer may be for example 10 microns.

After the first soldering cycle, the metal solder 10 is applied, for example in the form of a relatively viscous paste on the soldered or soldered Active solder layer is applied. In this case, the metal solder 10 readily the Wet the metallic surface of the active solder layer. Subsequently, a driven second solder cycle, in turn, the metal component 1 and the Soldering layers are heated. Through this soldering process can now be the Form the diffusion joints 11 between active solder 7 and metal solder 10.

The active metal of the respective active solder 7 reacts with the non-metallic Reaction product 6, e.g. with an oxide. This forms a reaction layer with a metallic surface, that is, from a conventional metal solder 10 is wettable. A wettable reaction layer can be 1 to 5 μm thick be. The metal solder 10 may be, for example, a wide-gap solder, the one Contains metal filler. The metal solder 10 may be on the soldered by the active solder 7 formed, consistently clean and wettable surface gapless spread. This gapless distribution of the metal solder 10 leads to a significant quality improvement of the filling, by the Hochtemperaturlötverfahren to repair the damaged area 2 has been applied is.

During the soldering cycles, the metal component 1 and the respective solder 7, 10 e.g. heated to about 1,000 ° C, so that this is a Hochtemperaturlötverfahren is.

After the second soldering cycle, a voltage annealing cycle can be performed where voltages created by the soldering cycles be reduced. Subsequently, in particular, the surface of the 10 metal brazes are processed, for example, the surface of the Match the repair point to the original contour of the metal component 1.

LIST OF REFERENCE NUMBERS

1

metal component

2

damaged area

3

Surface of 1 in 2

4

mountain

5

valley

6

reaction product

7

active solder

8th

Diffusion connection between 7 and 1

9

Reaction compound between 7 and 6

10

metal solder

11

Diffusion connection between 10 and 7

Claims (12)

1. Method for repairing a damaged area (2), formed by loss of material, on the surface of a metal component (1), the damaged area (2) being filled by means of a high-temperature brazing process, characterized in that an active brazing alloy (7) is used in the high-temperature brazing process.
2. Method according to Claim 1, characterized in that a metal filler is admixed with the active brazing alloy (7).
3. Method according to Claim 1 or 2, characterized in that the active brazing alloy (7) is admixed with a standard metal brazing alloy (10).
4. Process according to one of Claims 1 to 3, characterized in that a layer of active brazing alloy (7) is applied to the damaged area (2) and in that a layer of a standard metal brazing alloy (10) is applied to this active brazing alloy layer.
5. Method according to Claim 4, characterized in that the active brazing alloy layer and the metal brazing alloy layer are brazed in a single brazing cycle.
6. Method according to Claim 4, characterized in that the active brazing alloy layer is brazed prior to the application of the metal brazing alloy layer, in a first brazing cycle, and in that the metal brazing alloy layer is brazed after it has been applied, in a second brazing cycle.
7. Method according to one of Claims 4 to 6, characterized in that the active brazing alloy (7) and the metal brazing alloy (10) are each in the form of a paste, the active brazing alloy paste having a low viscosity relative to the metal brazing alloy paste.
8. Method according to one of Claims 1 to 7, characterized in that the active brazing alloy (7) is formed at or in the damaged area (2) by applying firstly an active metal and then a standard metal brazing alloy (10) to the damaged area (2).
9. Method according to one of Claims 3 to 8, characterized in that a metal filler is admixed with the metal brazing alloy (10).
10. Method according to one of Claims 1 to 9, characterized in that the metal component (1) is part of a turbomachine.
11. Method according to Claim 10, characterized in that the turbomachine is a turbine or a compressor.
12. Method according to Claim 10 or 11, characterized in that the metal component (1) is a blade or vane of the turbomachine.

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